93 mercruiser 350 dies ~40% of the time when shifting to N

[Biggyniner]

Hi guys,

right off the bat, it’s not the intermediate cable (replaced last year) and not shift interrupt switch (just replaced). Has new carb... Choke, idle mix and Idle speed adjusted and set to spec. Timing to spec, and newish spark plugs. Shift cables adjusted to factory spec. New cap and rotor. Engine replaced end of last season has 8 hours on it.

Tomorrow my boat mechanic and I are going to check compression.

Our theory on why this is happening is possibly a weak spark or other condition with the ignition (thunderbolt 4). He says he is at a loss and I don’t really just want to start throwing parts at it. Tried band-aiding it with higher idle by a couple hundred rpms, still will stall on occasion.

does anyone have any ideas or theories.. any help is appreciated.

thx

 

[achris]

Any chance of a little more detail? What drive? Engine serial number?

I would be watching the shift interrupt switch when it happens. Yes, you replaced the cable and the switch, but the lever and lever spring can also be the problem. If it was stalling from Neutral to Forward, I would believe it could be an engine problem, but from gear to neutral can only be the shift system... You're REMOVING load from the engine not adding it. If an engine is running, removing load will not stall it.

Does it do it only in the water or does it do it on flushers too?

Chris.......

 

[Biggyniner]

Any chance of a little more detail? What drive? Engine serial number?

I would be watching the shift interrupt switch when it happens. Yes, you replaced the cable and the switch, but the lever and lever spring can also be the problem. If it was stalling from Neutral to Forward, I would believe it could be an engine problem, but from gear to neutral can only be the shift system... You're REMOVING load from the engine not adding it. If an engine is running, removing load will not stall it.

Does it do it only in the water or does it do it on flushers too?

Chris.......

Drive is early gen 2 alpha 1 (no remote fluid reservoir). I’ll have to get back to you on a serial for drive. Engine serial is kind of moot as the original 305 was replaced with a 350. Haven’t had a chance to pull boat and test it on flushers. I never recall it stalling however on the hard when we were testing it end of last year.

the lever comes right off the bump immediately and the cable moves like butter. The switch we replaced it with was used however since they are discontinued...

 

[Bt Doctur]

remove the tach wire from the coil . the lever comes right off the bump immediately and the cable moves like butter. If on land you have binding in the shift cable system. Switch never operates on land

 

[Biggyniner]

remove the tach wire from the coil . the lever comes right off the bump immediately and the cable moves like butter. If on land you have binding in the shift cable system. Switch never operates on land

Not sure I am following you. Are you saying to pull the tach-wire off the coil and see if that cures my stall when shifting to N? What is the theory behind that, just curious?

 

[Bt Doctur]

to different answers, I had a cust boat that would just stall shifting into reverse. For some unknown reason I never found, removing the tack wire cured the stalling . 2nd, the shift interupter never operates on a trailer ,unly in the water ,under a load. There is a SB on replacing the spring of the iuntrupter to fix a stalling issue, factory spring was a bit weak